1. Field of the Invention
The present invention relates generally to light guide illumination systems and, more particularly, to air circulation cooling devices for use with light guide illumination systems.
2. Description of Related Art
Large diameter fiber optics, often referred to as "flexible light guides", are well known in the art, and typically comprise a single, solid core light guide which is surrounded by a cladding layer and a sheath or shielding layer. The core is the portion of a light guide which transmits light, and typically has a diameter of about 2 to 12 mm. It is formed of a very soft, semi-liquid plastic material, such as OPTIFLEX.RTM., which is manufactured by Rohm & Haas Corporation, of Philadelphia, Pa. The cladding layer typically comprises polytetrafluoroethylene (PTFE or TEFLON.RTM.), or the like, while the outer sheath is fabricated of a material such as polyvinylchloride (PVC). Unlike small diameter light guides, which are typically used to transmit information in relatively complex control systems, these large diameter "light guides" are typically employed in a variety of illumination systems where direct lighting is difficult to maintain, dangerous, or subject to vandalism. Examples include architectural lighting, display cases, pools and spas (to eliminate electrical connections near water), hazardous material zones (to eliminate the need for sealed lighting), and jail cells. Large diameter light guides are particularly advantageous in that only a single centralized illumination system must be maintained, rather than a plurality of individual lights.
There are problems, however, in implementing state of the art light guide illumination systems because of the difficulty of illuminating a plurality of light guides from a single illumination source, as is discussed in U.S. Pat. No. 5,559,911, which is expressly incorporated by reference herein. According to one prior art configuration, the light guides are bundled as closely as possible, to ensure the maximum ratio of core area (the part of each light guide which actually transmits light) to total area. However, bundling the large diameter light guides together in order to illuminate them from the single illumination source is difficult to do efficiently. The individual light guides are round and thus have a great deal of space between them due to the cladding and shielding layers. To obtain maximum efficiency, it is desirable to illuminate only the core of each of the bundled light guides, but this is impossible using state of the art bundling techniques. Necessarily, if the light from the source of illumination is spread across the array of light guides, it will illuminate not only the cores of the light guides, but also the cladding layers and shielding layers. Furthermore, the voids between the light guides, which are inevitable because of the light guides' round dimensions, also are impacted by the light from the illumination source. All of the light falling upon any element other than the cores is wasted, and becomes an efficiency loss, since it will not be transmitted by the light guides.
Light falling on elements other than the cores of the light guides generates heat thereon, which is undesirable. This heat on the ends of the light guides if too great will need to be dissipated, requiring additional equipment. Since the coupling of the light into the light guide bundle generates heat, an air duct is used to siphon a portion of an air stream, which is used to cool the arc lamp, to the coupling end of the light guide bundle. After the air from the air duct cools the coupling of the light guide bundle, the air can be routed back to provide additional cooling to the arc lamp.
A number of prior art approaches use reflectors for focussing light from a source of illumination into one or more light guides. U.S. Pat. No. 5,222,793 and U.S. Pat. No. 5,259,056, both to Davenport et al., disclose lighting systems which use a single reflector assembly for illuminating light transmissive elements. U.S. Pat. No. 5,396,571 to Saadatmanesh et al. discloses a multi-segmented lens which divides light from a light beam into four separate beams, each of which is focussed onto a separate light guide. U.S. Pat. No. 4,912,605 to Whitehead discloses an electric light source mounted between two reflectors, each of which directs light into a corresponding light guide. U.S. Pat. No. 5,469,337 to Cassarly et al. discloses a light source and a plurality of curved reflectors for focussing light into lenses and then into a plurality of light guides. The use of reflectors and multi-segmented lenses by the prior art for coupling light into light guides has represented some advancement over the prior art bundled light guides, but the need for a proper and efficient coupling of a light source to a plurality of light guides still remains.
Another problem associated with prior art designs is the large number of optical components associated with these designs. Reducing the number of parts of any optical design would appear to be advantageous to any system.